Various dielectric films have been formed in the past during the fabrication of semiconductor devices. For example, films such as silicon dioxide and silicon nitride have been used for dielectric films in the formation of capacitors, such as for memory devices, including dynamic random access memories and static random access memories. Such films typically have small leakage currents associated therewith.
With the shrinkage of minimum feature sizes of semiconductor devices, the requirement of providing high capacitance with thinner films is becoming apparent. As the dielectric constant of silicon dioxide and silicon nitride are relatively low, the need for utilizing higher dielectric constant films, such as tantalum pentoxide (Ta2O5), strontium titanate oxide (SrTiO3), and barium strontium titanate (BaxSr1-xTiO3) arises. Such high dielectric films provide the ability to achieve a larger capacitance value in a smaller area, i.e., with a thinner dielectric film.
However, conventional deposition processes for forming such high dielectric constant films result in films having leakage current levels that are unacceptable for semiconductor devices being fabricated. As described in the article entitled, “Leakage Current Mechanisms of Amorphous and Polycrystalline Ta2O5 Films Grown by Chemical Vapor Deposition,” by Aoyama et al., J. Electrochem. Soc., Vol. 143, No. 3, March 1996, various treatments have been carried out after Ta2O5 film deposition to reduce the leakage current thereof For example, such treatments described included dry O2 treatment, dry O3 treatment, O2 treatment with utilization of ultraviolet exposure, O3 treatment with use of ultraviolet exposure, and N2O plasma treatment. The results from the paper indicate that the presence of impurities, such as carbon and hydrogen, remaining in the Ta2O5 film leads to generally high leakage current and that oxidation of such impurities results in the reduction of the leakage current. However, post-deposition oxidation of such impurities results in a fabrication step generally not applicable to other dielectric films such as silicon dioxide and silicon nitride. Such post-deposition oxidation of high dielectric films, hereinafter referred to generally as post-deposition oxygen anneal, in addition to reducing throughput of devices also increases the thermal budget for fabrication of the devices.
Therefore, there is a need in the art for high dielectric oxide film formation methods and apparatus for forming high dielectric films, reducing throughput of devices by eliminating steps in the deposition process. The present invention provides such methods and apparatus for overcoming the problems as described above and other problems that will be readily apparent to one skilled in the art from the description of the present invention below.